There is another level of nuance in the joke though. You need to have had spent some time in a Eastern European country. Everyone is a stickler for rules, details, and knowing the "correct" answer, even if in practice, in a given situation, it makes no difference at all.
All shops were named "Shop" or "Gastronome", so come in, look around at merchandise and then understand what kind of shop it is, which was hard to do when no merchandise was left at all.
There also must be a play on words in original (untranslated) joke. "You don't have any meat?" in russian can be understood as "Do you have any meat?" and as "Is it your shop that has no meat?".
There is another level of nuance in the joke though. You need to have had spent some time in a Eastern European country. Everyone is a stickler for rules, details, and knowing the "correct" answer, even if in practice, in a given situation, it makes no difference at all.
This joke brings out that quality very nicely.